For the protection of the public, safety markers are required by law when moving wide machinery along public highways. The type of safety marker required (i.e. flag, reflector, or flashing light) depends upon surrounding circumstances, such as conditions of visibility. It is often difficult to permanently suspend a safety marker to such machinery.
By way of illustration, consider agricultural machinery, such as a chisel plow. The chisel plow is made with "wings" which are raised during transport. The plow must be moved from field to field via public highways. The law requires that a safety marker be placed on each side to clearly mark the sides of such wide machinery. In order to move the chisel plow, the wings are raised exposing the "working end" of the plow. In order to fulfill the legal requirements, the farmer is supposed to temporarily attach safety markers to the working end of the agricultural implement. Many farmers do not wish to take the time to make such a temporary installation and as a result accidents are occurring. A permanently installed safety marker is required for such machinery. The problem is that during use the "wings" of the chisel plow move up and down following the contours of the terrain. Any rigidly secured safety marker would be severed by the wing frame. It is for this reason that it has not been thought possible to permanently affix a safety marker to such machinery.